Brominated alkyl promotes a red-emissive probe track lipid droplets in cells and fatty liver

Lipid droplets (LDs) participate in lipid storage and metabolism, which is a critical indication of metabolic diseases, like nonalcoholic fatty liver disease (NAFLD). Fluorescent probes have been extensively applied due to their excellent superiorities, but it is usually impossible to realize specific LDs-targeting by a simple bromination in a fluorescent probe. In current study, we developed two red-emissive probes (G1 and G2) that are condensed by isophorone and carbazole with or without a bromine substitution in alkyl group. Unexpectedly, G1 with brominated alkyl displayed specific targeting to LDs, while G2 with only alkyl chain exhibited no LDs-targeting effect. Subsequently, G1 was successfully applied to track LDs and their dynamics in living cells, and image LDs in livers of mice feeding high-fat diet. This study is a new paradigm for devising a fluorescent tool to trace LDs, which provides a powerful tool for the early diagnosis of NAFLD.